The present invention relates to a data processing unit, such as a microprocessor or microcontroller, with debug capabilities. Whereas in the first microprocessor systems debugging of software could only be done by software which did not allow any real time analysis, nowadays microprocessors have special debug hardware on chip. This debug hardware allows to program breakpoints to control the flow of a program which has to be analyzed. Therefore, the breakpoints do not have to be simulated by software anymore, but still even hardware generated breakpoints may interrupt the program and control will be taken by the respective debug software. In many real time applications, program flow may not be interrupted. Thus, for many real time applications an in circuit emulator might still be necessary.